Widening bore of tubular bend



June 24, 1958 A. HUET WIDENING BORE OF TUBULAR BEND Filed Dec. 14, 1951 INVEN United States Patent 2,839,818 WIDENING BORE or TUBULAR BEND Andre Huet, Paris, France, assignor to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Application December 14, 1951, Serial No. 261,666

1 Claim. (Cl. 29157.6)

The present invention relates to tube bending and particularly to an improved method of providing 180 return bends with closely spaced tube lengths.

In an earlier application filed on May 13, 1949 under Serial No. 92,994 now Patent No. 2,689,596 applicant has disclosed an improved method for decreasing the spacing of the legs or tube lengths contiguous'to elbows or bends in tubes or pipes previously bent on a certain radius of curvature. Where the tubes are of large diameter, or have a relatively great wall thickness, the application of methods of decreasing tube spacing by external stress exerted on the legs of the elbow is often found diflicult because of the increased thickness of metal that exists in the crotch region of the bend, which results from making the bend, for example, by rolling a straight tube on a bending roller.

The subject of the present invention is a method which permits, nevertheless, of bringing closer together the tube lengths of return bends even in case of thickened crotch regions the method being particularly applicable to elbows, or bends, which have a neck, that is to say an open connection in the external region of the bend. According to the invention, this opening is utilized to introduce a punch into the bend, the punch having two converging fork-shaped prongs which cap the central part, or inside of the crotch region of the bend. The bend may be previously heated, and the stress exerted by the punch makes it possible to effect, directly inside the elbow, the bringing together of the two legs of the bend. V

This method may be carried out in combination with a method as in the aforesaid application of bringing together the legs of the bend with the aid of dies acting externally on said legs, as well as with a shaping process of the neck made in the bend by means of suitable dies.

The description which follows when read with respect to the attached drawing will make the manner of executing the invention more understandable.

Figure 1 shows in section a bend having a neck, and of which it is proposed to draw together the leg portions contiguous to the bend.

Figure 2 is a sectional view showing the bend of Fig. I placed in the dies and a punch introduced for the execution of the method of the invention.

Figure 3 shows the state of the bend after driving in the punch and the bringing together of the legs of the bend.

The bend a having a neck b for connection of another tube in the end of the elbow has at c an increased -wall thickness in the crotch region of the bend. This increased thickness could oppose the effort for bringing closer together the legs d of the bend where it is desired to finally have a band with legs very close together.

According to the invention, the presence of the open neck b makes it possible to introduce, into the interior of the bend, a punch 10 terminated in two converging prongs 11, 12 like a fork, and which cap or embrace the crotch region 0 of the bend, as shown in Figure 2. By then exerting pressure on the punch in the direction of the arrow A, preferably after a preliminary heating of the crotch region 0 of the bend, one causes narrowing of the spacing of the two inner wall sections 1 of the parallel legs d of the bend.

This method may be carried out in combination with the process of the aforesaid application, according to which dies 13, 14 press against the outside parts h of the two legs of the bend in a bringing-together movement acting in the direction of arrows B B.

One can also combine with this method a process of shaping the neck b of the bend. This neck may be brought to the desired interior diameter, by using a cylindrical punch 10, while a sleeve 15 acts as a stop against the edge of the neck'b while the dies 13, 14 are shaped at 16 so as to give the desired shape to the neck externally. In this case the process can be combined with a heating of the region of the bend corresponding to the neck.

After bringing together the dies 13, 14 concurrently with the driving in of the punch 10, one produces finally, as may be seen in Figure 3, a bend having a neck and with the legs d of the bend brought together to the point of being almost in contact.

As has been said, the method is particularly applicable to the case in which one treats elbows made in tubes of large diameter, and of relatively great thickness of wall. It has the advantage of combining for the bringing to gether of the legs of the bend, an eifort exerted externally on the legs of the bend with an effort exerted inside of the bend, on the walls of the legs located in the inside region of the bend.

What I claim is:

The method of narrowing the spacing of the tubular legs contiguous to the elbow of a bend integrally formed in a metallic tube and having an open neck on the end of the elbow which comprises; suitably heating the crotch region of the bend; introducing into the neck of the elbow a punch having two convergent prongs separated by a relatively deep recess of a width less than the spacing of the adjacent inner wall surfaces of the tubular legs; exerting pressure on the punch and displacing it axially within the elbow toward the crotch thereof to bring the base of the recess between said prongs substantially into contact with the internal crotch region of the elbow and with the tube leg portions contiguous to said elbow and thereby move closer together the confronting wall portions of the tube legs contiguous to the elbow; and decreasing the spacing of the outwardly located portions of the tube legs contiguous to the elbow by applying oppositely acting forces against the external regions of the legs, whereby the combined action of the punch and said forces elfects a decrease in the spacing of the axes of said tube legs.

References Cited in the file of this patent UNITED STATES PATENTS 1,255,355 True Feb. 5, 1918 1,442,481 Lassiter Jan. 16, 1923 1,924,891 True Aug. 29, 1933 

